Lamp mounting bracket

ABSTRACT

A lamp mounting bracket is described which allows longitudinal and torsional strains to be relieved due to differential expansion between lamp and mounting frame. The mounting bracket is particularly useful in mounting ultraviolet light emitting lamps in ultraviolet light processors designed to cure ultraviolet light sensitive coatings.

[451 Sept. 16, 1975 United States Patent [1 1 Lackore LAMP MOUNTING BRACKET [75] Inventor: James Kneeland Lackore, Mount Prospect, Ill.

[73] Assignee: PPG Industries, Inc., Pittsburgh, Pa.

[22] Filed: Mar. 14, 1974 21 Appl. No.: 451,253

Primary Examiner-Richard A. Wintercom Attorney, Agent, or Firm-George D. Morris ABSTRACT [52] US. 240/51.l1; 240/52.l; 240/73 R; 339/50 R; 339/54 H05B 33/02; F2-1V 21/08;

HOlR 33/08;H01R 33/10 [51] (31-2 A lamp mounting bracket is described vvhich allows longitudinal and torsional strains to be relieved due to differential expansion between lamp and mounting [58] Field of Search.............. 240/73 R, 52.1, 51.11, frame The mounting bracket is particularly useful in 240/1 1.4; 339/50 R, 52 R, 52.1, 55, 54; 313/49-51 mounting ultraviolet light emitting lamps in ultraviolet light processors designed to cure ultraviolet light sensitive coatings.

[56] References Cited UNITED STATES PATENTS 2,595,515 5/1952 339/54 15 Claims, 7 Drawing Figures LANIP MOUNTING BRACKET This invention relates to a lamp mounting bracket and to ultraviolet light coating processors employing such a lamp mounting bracket.

The use of ultraviolet light processors to cure ultraviolet light sensitive coatings is becoming more widespread. Advantages of ultraviolet light curing include the ability to use resin systems which have little or no volatile solvents, the speed with which cure may be accomplished and the simplicity of operation. Several problems have been encountered in mounting ultraviolet light emitting lamps in the processors.

One disadvantage is that most ultraviolet light emitting lamps used in processors give off a good deal of heat. These lamps are usually of the metal halide seeded, medium or high pressure mercury vapor type. Such lamps usually have fused quartz envelopes to withstand the heat and transmit the ultraviolet radiation and are ordinarily in the form of long tubes having an electrode at either end. Examples of these lamps are PPG Models 60-2032, 60-0393, 60-0197 and 60-2031 and Hanovia Models 6512A431, 6542A431, 6565A431 and 6577A431. The lamps are usually held in place by electrically insulated mounting brackets on the ends. The frame, which may include a reflector depending upon the details of construction, is ordinarily fabricated from a metal so that it too may withstand the heat. Most structural metals have high coefficients of thermal expansion whereas fused quartz, of course, has a very low such coefficient. The differences in expansions and contractions during start-up and shut-down of the apparatus set up strains in the lamp. If the lamp is tightly held at both ends, a broken envelope is frequently the result. If the lamps are not held tightly enough, they sometimes drop out of their mounting brackets.

Another disadvantage to improperly mounting a lamp is poor electrical contact. Most of the lamps described above draw rather large currents, say on the order of from about to about amperes at voltages usually in the range of from about 500 to about 3000 volts A.C. Direct current may also be used. If the lamps are too loosely held, the areas of electrical contact between the lamp mounting lug and the mounting bracket will be small. These small areas give rise to high resistances which consume inordinate amounts of power and are sources of large amounts of heat.

This invention contemplates a lamp mounting bracket which is free to move longitudinally parallel to the axis of the lamp while holding the lamp mounting lug firmly enough to provide good electrical contact.

For a better understanding of the invention, reference may be made to the drawings wherein like numerals refer to like parts in which:

FIG. 1 illustrates an appropriate embodiment of the invention together with the end portion of a typical ultraviolet emitting tube;

FIG. 2 is a frontal view of the embodiment of FIG. 1;

FIG. 3 is a cross-sectional view of the base of the embodiment of FIG. 1;

FIG. 4 is a plan view of the yoke of the embodiment of FIG. 1;

FIG. 5 is an exploded view of the parts making up the embodiment of FIG. 1;

FIG. 6 illustrates the embodiment of FIG. 1 with the typical ultraviolet light emitting tube installed; and

FIG. 7 is a frontal view of FIG. 5.

The lamp mounting brackets of the present invention have a base, electrically conductive compression means for engaging portions of the cylindrical mounting lug of a lamp and means for loosely retaining the electrically conductive compression means to the base so that the electrically conductive compression means can freely move with respect to the base in a direction parallel to the axis of the electrically conductive cylindrical mounting lug without disengaging the mounting lug.

Referring now to the FIGURES where the invention will for convenience be described with respect to an embodiment thereof, a lamp mounting bracket suitable for use in the practice of this invention includes a base 1 having mounting holes 2,2 and hole 4. This base is usually made of an electrically insulating material such as ceramic, glass, synthetic plastic, wood, and the like. Ceramic and glass are preferred because of their additional resistance to heat. If electrically insulated from other mounting brackets where a different electrical potential is applied to the lamp, the base may be made of an electrically conducting material such as metal. The metals referred to herein are those commonly used for structural purposes and whichare reasonably stable under the conditions of use. Examples include copper, brass, bronze, iron, steel, aluminum, titanium, gold, silver, platinum, palladium, tungsten, molybdenum, vanadium, manganese, cobalt, niobium, zinc and the like. Base 1 is conveniently made of ceramic and may advantageously have a conical recess 6. The remaining parts are usually made of an electrically conducting material such as metal. Screw 8 passes through hole 4 of base 1. Washer 10 is placed on screw 8 and the screw is held in place by nut 12. Yoke 14 is positioned atop nut 12 by passing screw 8 through slot 16. Yoke 14 is loosely retained in place by locknut l8 engaging screw 8 such that yoke 14 is free to slide longitudinally along slot 16 and to rotate about screw 8. The rotational freedom around screw 8 and the presence of a small amount of play in planes containing the axis of screw 8 also permit relief of strains which might otherwise build up in these directions. Moderate amounts of thermal warping of the housing members can be accommodated by these features.

Screws 20 and 22 pass through holes 24 and 26, respectively, of yoke 14. Preferably holes 24 and 26 are tapped so that the screws are engaged by these holes. Cradle 28, having generally right circular cylindrical surface 29, rests on yoke 14 with screws 20 and 22 passing through holes 30 and 32 located near opposite ends, respectively. It is preferred that holes 30 and 32 be larger than the screws passing therethrough so that the fit is a loose one and some play is present. It is also preferred that cradle 28 be of a resilient material such as nickel plated brass.

Retainer 34 is positioned above cradle 28 with screws 20 and 22 passing loosely through hole 36 and opening 38, respectively, which are located near opposite ends of the retainer. Opening 38 is significantly larger than the diameter of screw 22 so that the retainer does not bind on screw 22 when compressed as hereinafter described. Opening 38 may conveniently take the form of a slot. The longitudinal axis of such slot and the axis of the generally right circular cylindrical surface 29 of right angles. The retainer of the embodiment illustrated in the drawings has an offset 39.

Yoke 14, cradle 28 and retainer 34 are held in place by nut 40 engaging screw 20 and by nut 42 engaging screw 22. Nut 40 cooperates with screw 20 to hold yoke 14, cradle 28 and retainer 34 together near their respective ends, and, by the added cooperation of offset 39, to tend to hold retainer 14 and generally right circular cylindrical surface 29 of cradle 28 apart. Nut 42 is capable of moving along the axis of screw 22 to move retainer 34 and generally right circular cylindrical surface 29 into closer proximity. Nuts 40 and 42 -may be ordinary hexagonal nuts, square nuts, wing nuts, or similar such nuts, but it is preferred that they be binding post nuts.

Electrical energy may conveniently be supplied to the mounting bracket by connecting a conductor, such as a copper wire, from a source of electrical energy to screw 20 prior to tightening nut 40.

Lamp mounting brackets of this invention are particularly useful for holding ultraviolet light emitting lamps having cylindrical mounting lugs through which electrical current passes to the electrodes contained inside. Examples of such lamps have been listed above. An exemplary such lamp is lamp 50, a portion of which is shown in the drawings, having an envelope 52, usually of fused quartz. Stem 54 generally comprises a fused quartz body having a metallic conductor not shown, passing longitudinally therethrough for conducting electrical current to an electrode, also not shown, inside envelope 52. The conductor is also in electrical contact with cylindrical mounting lug 56. Smaller cylindrical mounting lug 58 is often found on the end of cylindrical mounting lug 56. FIGS. 5 and 6 show the lamp mounting bracket holding one end of a lamp of the type just described.

. Referring especially to FIG. 6, it may be seen that there are areas of contact between cylindrical mounting lug 56 on the one hand and cradle 28 and retainer 34 on the other. Contact is improved if cradle 28, retainer 34 or both of them are made of a resilient metal which will deform slightly under the compression provided by nuts 40 and 42 being tightened down on screws and 22 respectively. Nickel plated brass is a particularly preferred material. The deformation may be elastic or non-elastic, but the former is preferred. When cylindrical mounting lug 56 is about A: inch in diameter and about inch long, cradle 28 and retainer 34 are advantageously constructed of nickel plated brass sheet about 1/32 inch thick. Yoke 14 is normally made of heavier material such as steel or nickel plated brass about 3/32 inch thick.

In practice, cylindrical mounting lug 56 is rested in cradle 28 and nut 40 is tightened finger tight. Nut 42 is tightened to the point that good electrical contact of the parts is made. Preferably nut 42 is tightened so that cylindrical mounting lug 56 may rotate around its axis between cradle 28 and retainer 34 upon the application of moderate torsional stress to thereby relieve the torsional strain. If torsional stress is of a minor nature or of a secondary consideration, even better electrical contact may be achieved by further tightening of nut 42. It will be observed that as the tightening force increases, the retainer tends to wrap around the cylindrical mounting lug and the cradle tends to deform into closer contact with the mounting lug. Both phenomena increase the area of contact and reduce the resistance at these points.

An additional benefit gained through use of the lamp mounting bracket of the present invention to dissipation of heat. The mounting bracket, being in contact with the cylindrical mounting lug of the lamp, increases considerably the surface area from which heat may be removed. It is particularly effective, in this respect when the yoke, cradle and retainer are all fabricated from sheet metal.

It is preferred that lamp mounting brackets of this invention be used to mount lamps at both ends thereof, but this is not necessary. It may be desired, for instance, to replace slot 16 of one lamp mounting bracket with a hole so that substantially all longitudinal strain is relieved by movement in slot 16 of the lamp mounting bracket at the opposite end of the lamp.

While the foregoing description has particular reference to ultraviolet light coating processors, the lamp mounting bracket of the present invention has general utility and may be employed for these purposes. For example, the lamp mounting brackets may be used to hold lamps around their fused quartz stems while other connectors which supply electrical energy are attached to the lamp mounting lugs. Asbestos cloth or other heat resistant resilient material is ordinarily first wrapped around the stem when practicing this embodiment.

It is apparent that many widely different embodiments of this invention can be made without departing from the spirit and scope thereof, and, therefore, it is not intended that the invention be limited except as indicated in the appended claims.

I claim:

1. A lamp mounting bracket comprising A. a base;

B. electrically conductive compression means for engaging portions of the cylindrical surface of an electrically conducting cylindrical mounting lug of a lamp; and

C. means for loosely retaining said electrically conductive compression means to said base so that said electrically conductive compression means can freely move with respect to said base in a direction parallel to the axis of said electrically conductive cylindrical mounting lug without disengaging said mounting lug.

2. The lamp mounting bracket of claim 1 wherein said base is electrically insulating.

3. A lamp mounting bracket comprising A. a base;

B. a yoke slidably fastened to said base;

' C. a cradle fastened to said yoke, said cradle having a generally right circular cylindrical surface wherein the axis of said generally right circular cylindrical surface is generally parallel to a direction in which said yoke is free to slide with respect to said base;

D. a retainer which is l. fastened to said cradle and said yoke, and 2. spaced apart from said generally right circular cylindrical surface of said cradle; and

E. means for moving said retainer and said generally right circular cylindrical surface into closer proximity.

4. The lamp mounting bracket of claim 3 wherein said base is electrically insulating.

5. The lamp mounting bracket of claim 3 wherein said cradle is electrically conductive.

6. The lamp mounting bracket of claim 3 wherein said retainer is electrically conductive.

7. The lamp mounting bracket of claim 3 wherein said cradle is resilient.

8. The lamp mounting bracket of claim 3 wherein said retainer is resilient.

9. The lamp mounting bracket of claim 3 wherein said retainer has an offset.

10. A lamp mounting bracket comprising A. an electrically insulating base having a hole therein;

B. a first screw passing through said hole in said base and being fixedly retained by a first nut engaging said first screw;

C. a yoke having therein 1. a slot, and 2. two tapped holes near opposite ends of said yoke, wherein said first screw passes through said slot; D. a locknut engaging said first screw to retain said yoke on said first screw and to allow said yoke to move freely with respect to said base in the direction of the longitudinal axis of said slot; E. a second screw threaded into the first of said tapped holes in said yoke; F. a third screw threaded into the second of said tapped holes in said yoke; G. an electrically conductive resilient cradle having two holes near opposite ends thereof and having a generally right circular cylindrical surface between said two holes, wherein 1. said second screw passes through the first of said holes in said cradle,

2. said third screw passes through the second of said holes in said cradle, and

3. the axis of said generally right circular cylindrical surface is generally parallel to the longitudinal axis of said slot in said yoke;

H. an electrically conductive resilient retainer having 1. a hole near one end thereof,

2. an opening significantly larger than the diameter of said third screw near the opposite end thereof, and

3. an offset between said hole and said opening wherein 4. said second screw passes through said hole in said retainer, and

5. said third screw passes through said opening in said retainer;

I. a second nut engaging said second screw and cooperating therewith 1. to hold said yoke, said cradle and said retainer together near the respective ends thereof, and

2. by the added cooperation of said offset, to tend to hold said retainer and said generally right circular cylindrical surface of said cradle apart;

and

J. a third nut engaging said third screw and being capable of moving along the axis of said third screw to move said retainer and said generally right circular cylindrical surface of said cradle into closer mutual proximity.

11. The lamp mounting bracket of claim 10 wherein said second and third nuts are binding post nuts.

12. The lamp mounting bracket of claim 10 wherein said cradle and said retainer are of nickel plated brass.

13. In an ultraviolet light coating processor having means for mounting at least one ultraviolet light emitting lamp, the improvement wherein at least one of said means for mounting is the lamp mounting bracket of claim 1.

14. In an ultraviolet light coating processor having means for mounting at least one ultraviolet light emitting lamp, the improvement wherein at least one of said means for mounting is the lamp mounting bracket of claim 3.

15. In an ultraviolet light coating processor having means for mounting at least one ultraviolet light emitting lamp, the improvement wherein at least one of said means for mounting is the lamp mounting bracket of claim 10. 

1. A lamp mounting bracket comprising A. a base; B. electrically conductive compression means for engaging portions of the cylindrical surface of an electrically conducting cylindrical mounting lug of a lamp; and C. means for loosely retaining said electrically conductive compression means to said base so that said electrically conductive compression means can freely move with respect to said base in a direction parallel to the axis of said electrically conductive cylindrical mounting lug without disengaging said mounting lug.
 2. The lamp mounting bracket of claim 1 wherein said base is electrically insulating.
 2. two tapped holes near opposite ends of said yoke, wherein said first screw passes through said slot; D. a locknut engaging said first screw to retain said yoke on said first screw and to allow said yoke to move freely with respect to said base in the direction of the longitudinal axis of said slot; E. a second screw threaded into the first of said tapped holes in said yoke; F. a third screw threaded into the second of said tapped holes in said yoke; G. an electrically conductive resilient cradle having two holes near opposite ends thereof and having a generally right circular cylindrical surface between said two holes, wherein
 2. said third screw passes through the second of said holes in said cradle, and
 2. an opening significantly larger than the diameter of said third screw near the opposite end thereof, and
 2. spaced apart from said generally right circular cylindrical surface of said cradle; and E. means for moving said retainer and said generally right circular cylindrical surface into closer proximity.
 2. by the added cooperation of said offset, to tend to hold said retainer and said generally right circular cylindrical surface of said cradle apart; and J. a third nut engaging said third screw and being capable of moving along the axis of said third screw to move said retainer and said generally right circular cylindrical surface of said cradle into closer mutual proximity.
 3. an offset between said hole and said opening wherein
 3. the axis of said generally rigHt circular cylindrical surface is generally parallel to the longitudinal axis of said slot in said yoke; H. an electrically conductive resilient retainer having
 3. A lamp mounting bracket comprising A. a base; B. a yoke slidably fastened to said base; C. a cradle fastened to said yoke, said cradle having a generally right circular cylindrical surface wherein the axis of said generally right circular cylindrical surface is generally parallel to a direction in which said yoke is free to slide with respect to said base; D. a retainer which is
 4. said second screw passes through said hole in said retainer, and
 4. The lamp mounting bracket of claim 3 wherein said base is electrically insulating.
 5. The lamp mounting bracket of claim 3 wherein said cradle is electrically conductive.
 5. said third screw passes through said opening in said retainer; I. a second nut engaging said second screw and cooperating therewith
 6. The lamp mounting bracket of claim 3 wherein said retainer is electrically conductive.
 7. The lamp mounting bracket of claim 3 wherein said cradle is resilient.
 8. The lamp mounting bracket of claim 3 wherein said retainer is resilient.
 9. The lamp mounting bracket of claim 3 wherein said retainer has an offset.
 10. A lamp mounting bracket comprising A. an electrically insulating base having a hole therein; B. a first screw passing through said hole in said base and being fixedly retained by a first nut engaging said first screw; C. a yoke having therein
 11. The lamp mounting bracket of claim 10 wherein said second and third nuts are binding post nuts.
 12. The lamp mounting bracket of claim 10 wherein said cradle and said retainer are of nickel plated brass.
 13. In an ultraviolet light coating processor having means for mounting at least one ultraviolet light emitting lamp, the improvement wherein at least one of said means for mounting is the lamp mounting bracket of claim
 1. 14. In an ultraviolet light coating processor having means for mounting at least one ultraviolet light emitting lamp, the improvement wherein at least one of said means for mounting is the lamp mounting bracket of claim
 3. 15. In an ultraviolet light coating processor having means for mounting at least one ultraviolet light emitting lamp, the improvement wherein at least one of said means for mounting is the lamp mounting bracket of claim
 10. 